The present invention relates to a dilatation catheter for use in angioplasty. Angioplasty has gained wide acceptance as an efficient and effective method of opening stenoses in the vascular system. In the most widely used form of angioplasty, a dilatation balloon catheter is guided through the vascular system until a balloon, which is mounted at the distal end of the catheter shaft, is positioned across the stenosis. The balloon is then inflated to open the artery and reestablish acceptable blood flow.
Dilatation catheters can generally be divided into those which are fed over a guide wire (i.e., "over-the-wire" catheters) and those catheters which serve as their own guide wire (i.e., "fixed-wire" catheters). Both types of catheters have advantages and disadvantages.
Innerless dilatation balloon catheters have been developed in an attempt to obtain some of the advantages of a fixed-wire catheter while still retaining the advantages of an over-the-wire catheter. These innerless catheters feature a shaft having a single lumen which acts as both an inflation lumen and a guide wire lumen. A lumen extension extends through the balloon, which is mounted on the distal end of the shaft. The shaft lumen is in fluid communication with the interior of the balloon. The guide wire extends through the shaft lumen, the lumen extension and out the distal end of the balloon.
Examples of innerless dilatation balloon catheters are shown in U.S. Pat. Nos. 5,032,113 and 5,035,705 by Matthew M. Burns.
When used in percutaneous transluminal coronary angioplasty (PTCA), the dilatation catheter is typically advanced through a guide catheter to the aorta. Using fluoroscopy, the physician manipulates the catheter until the balloon is located across the stenosis. This may involve the use of a guide wire over which the catheter is moved. Alternatively, the catheter may act as its own guide wire, depending upon the particular design. The manipulation of the dilatation catheter through the guide catheter and through the coronary arteries to the stenosis requires the dilatation catheter to have a number of different, sometimes conflicting, characteristics.
For example, a successful dilatation catheter must offer flexibility so that the catheter can maneuver through tight curvatures of the vascular system. A dilatation catheter also must allow the physician to transmit longitudinal force along the dilation catheter from its proximal end to its distal end so the catheter can be pushed through the guide catheter and arteries and across the stenosis. This characteristic is referred to as pushability. Typically, the outer dimensions of all parts of the dilatation catheter, including particularly the shaft, should be minimized. Friction between the dilatation catheter, the guide catheter and the guide wire, respectively, should also be minimized.
Prior dilatation catheters typically reflected trade-offs between these and other characteristics. For example, catheters having shafts with sections of different materials have been used in order to provide greater flexibility at the distal end of the catheter. Thin wall materials such as stainless steel hypo tubing and polyimide tubing have been used for proximal sections of dilatation catheter shafts in order to reduce the outer diameter and wall thickness of the catheter shaft.